Nitrogen Asphyxiation - medical breathing mask hooked up to a tank of 99% pure nitrogen. Add a brain activity monitor and turn on to 1.1 atmospheres. Then wait till there is no more brain wave activity.
Economical - A large tank of nitrogen is less than $100 and you can get several uses out of one tank
Clean - no gore, blood or other body fluids involved
Painless - the condemned falls asleep in a few seconds with no feeling of suffocation.
Yep. Nitrous Oxide is often the preferred method of suicide for Dentists. Painless. They are usually found in the patients’ chair with the mask on.